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https://issues.apache.org/jira/browse/HDFS-11242?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16870557#comment-16870557
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He Xiaoqiao commented on HDFS-11242:
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Thanks [~larsfrancke] for your quick response. IIUC, namenode will check if
replications of one block has enough racks based on PlacementPolicy when
namenode restart or failover. {{BlockManager#postponedMisreplicatedBlocks}}
could be one data structure which is related. Please double check and correct
me if something wrong.
As mentioned above, I prefer to design flexible rack aware script (refer to
https://hadoop.apache.org/docs/r3.2.0/hadoop-project-dist/hadoop-common/RackAwareness.html),
rather than have to specify proper rack when add new nodes.
Thanks again.
> Add refresh cluster network topology operation to dfs admin
> -----------------------------------------------------------
>
> Key: HDFS-11242
> URL: https://issues.apache.org/jira/browse/HDFS-11242
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Affects Versions: 3.0.0-alpha1
> Reporter: Reid Chan
> Priority: Minor
> Attachments: HDFS-11242.002.patch, HDFS-11242.patch
>
>
> The network topology and dns to switch mapping are initialized at the start
> of the namenode.
> If admin wants to change the topology because of new datanodes added, he has
> to stop and restart namenode(s), otherwise those new added datanodes are
> squeezed under /default-rack.
> It is a low frequency operation, but it should be operated appropriately, so
> dfs admin should take the responsibility.
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